Exploring, drilling, completing, and operating hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well access, monitoring and management throughout its productive life. Well intervention and ready access to well information may play critical roles in maximizing the life of the well and total hydrocarbon recovery. As a result, downhole tools are frequently deployed within a given hydrocarbon well throughout its life. These tools may include logging tools to provide well condition information. Alternatively, these tools may include devices for stimulating hydrocarbon flow, removing debris or scale, or addressing a host of other well issues.
The above noted downhole tools are generally delivered to a downhole location by way of a well access line. A well access line may include a wireline or slickline cable, coiled tubing, and other forms of downhole conveyance line. Regardless, once delivered downhole, a well application may proceed employing the tool. Subsequently, a winch-driven drum at the surface of the oilfield may be used to withdraw the well access line and tool from the well. Unfortunately, however, the well access line and/or tool often become stuck in place downhole. This may be due to the presence of an unforeseen obstruction, unaccounted for restriction, differential sticking of the tool against the well wall, or a host of other reasons.
In the case of wireline cable, a weak-point is generally built into the cable head where the tool and cable are joined. Thus, when sticking occurs, the winch may continue to pull uphole on the line until a break occurs at the weak-point. Subsequently, a fishing operation may ensue to retrieve the stuck tool from the well. Unfortunately, slickline, coiled tubing, and other conveyances often lack a built-in weak-point. Thus, at best, continued pulling on the line will only result in an uncontrolled break, generally nearer the oilfield surface. Such an uncontrolled break may leave the well obstructed by thousands of feet of line that will only add to the time, effort, and expense of the follow-on fishing operation. Furthermore, even where a weak-point is built into the assembly, break failure of the weak-point often occurs. This may be due to a design or manufacturing flaw, or other reasons. Regardless the reason, failure of the weak-point to break may result in an uncontrolled break as noted above.
In the case of wireline or other non-tubing conveyances, cutting bars are often employed in an attempt to avoid uncontrolled breaking of the line. A cutting bar is a pipe equipped with an internal cutting mechanism. The bar may be positioned over the line and dropped vertically into the well. In theory, the bar will drop until it reaches the sticking location, at which point the sudden stopping of the bar will actuate the cutting mechanism and induce a break in the line.
Unfortunately, employing a cutting bar may still result in breaking the line at a location uphole of the sticking location. This is due to the fact that the described cutting bar technique proceeds blindly. So, for example, in the case of a deviated well, the cutting bar will stop dropping and cut the line as soon as a bend or deviation is encountered which may be nowhere near the targeted sticking location. Similarly, a slight narrowing in the well, or minimal obstruction unrelated to the sticking of the line, may be enough to stop the fall of the cutting bar. Either way, the cutting bar may stop uphole of the sticking location, induce a break in the line, and add tremendous time and expense to the follow-on fishing operation.
As an alternative to the cutting bar, a timed cutter may be deployed within the well. That is, a cutter equipped with a cutting mechanism that is activated based on a timer may be dropped into the well. In this way, temporary stopping of the cutter, for example, upon encountering a minor obstruction, may not result in activation of the cutting mechanism. Rather, the cutting mechanism may be activated only after a set period of time, presumably after bypassing any such minor temporary obstructions.
Unfortunately, the use of a timed cutter fails to overcome uncontrolled line breaks in circumstances of deviated wells or in the face of significant well obstructions. In such cases, the activation of the cutting mechanism is still likely to take place well uphole of the sticking location. That is, the mode of cutting remains blind and thus, susceptible to breaking the line well uphole of the targeted sticking location. Furthermore, in the case of coiled tubing, similar cutting mechanisms may be employed that generally involve the initial deployment of a cable interior of tubing so that follow-on cutting techniques may be carried out. However, such techniques remain blind and susceptible to inducing coiled tubing breaks uphole of the targeted sticking location. In fact, in the case of coiled tubing, the cutting techniques generally require cutting of the coiled tubing at the location of the drum in order to deploy the interior cable. As a result, large amounts of coiled tubing are rendered ineffective for future use. Thus, in many cases, the operator may ultimately be left with no better option than to run a blind attempt at cutting the line which runs a significant likelihood of adding several hundred thousand dollars of expense to future fishing and other operations.